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package cn.taketoday.expression.parser;

import cn.taketoday.expression.ExpressionException;
import cn.taketoday.expression.LambdaExpression;
import cn.taketoday.expression.ValueExpression;
import cn.taketoday.expression.ValueExpressionImpl;
import cn.taketoday.expression.lang.EvaluationContext;

/**
 * @author Kin-man Chung
 */
public class AstLambdaExpression extends SimpleNode {

  public AstLambdaExpression(int id) {
    super(id);
  }

  @Override
  public Object getValue(EvaluationContext ctx) throws ExpressionException {
    final Node[] children = this.children;
    // Create a lambda expression
    final ValueExpression expr = new ValueExpressionImpl("#{Lambda Expression}", children[1], null);

    LambdaExpression lambda = new LambdaExpression(((AstLambdaParameters) children[0]).getParameters(), expr, ctx);

    if (children.length <= 2) {
      return lambda;
    }

    // There are arguments following the lambda exprn, invoke it now.
    Object ret = null;
    for (int i = 2; i < children.length; i++) {
      if (ret != null) {
        if (!(ret instanceof LambdaExpression)) {
          throw new ExpressionException("A Lambda expression must return another Lambda expression in this syntax");
        }
        lambda = (LambdaExpression) ret;
      }
      ret = lambda.invoke(ctx, ((AstMethodArguments) children[i]).getParameters(ctx));
    }
    return ret;
  }
}
